Process oe making materials containing tungsten



Patented Apr. 1.6, 1929.

UNITED STATES PATENT OFFICE.

HILAND G. BATCHELLER, OF ALBANY, AND JESS D. KELLEY, OF MENANDS, NEW YORK,

ASSIGNORS TO LUDLUM STEEL COMPANY, OF WATEEVLIET, NEW YORK, A COR- PORATION OF NEW JERSEY.

PROCESS OF MAKING MATERIALS CONTAINING TUNGSTEN.

No Drawing. Continuation of application Serial No. 5,888, filed January 30, 1925. This application filed October 6, 1925. Serial No. 60,912.

Our invention relates to a process of making materials containing tungsten including the making of materials for use in makng steels and other alloys containing tungsten, and'the production of such steels and other alloys themselves. a

The customary practice now followed in making alloy steels containing tungsten consists of the addition in the furnace of ferro tungsten in the solid state to a charge of steel in the amount calculated to give the desired tungsten content.

The customary practice now followed in making ferro tungsten for use in tungsten bearing steels consists of the reduction in an electric furnace of tungsten ore with carbonaceous material, such as coke, the ferro tungsten beginning with a button formed at the'bottom of the furnace and being built up gradually as reduction proceeds. Such a process does not permit the complete recovery of the tungsten contained in the ore,

'due to mechanicallosses and to tungsten losses in the slag that is formed. This slag is ordinarily reworked in much the same manneras the original. tungsten ore in order to recover the greatest possible proportion of tungsten from the ore. To the best of-our information, the loss of tungsten in the above process, even if the slag has been reworked as indicated, is from to of the tungsten contained in the ore. The ferro tungsten so made contains approximately 7 0% to 80% tungsten, carbon, the balance is principally iron.

It is not found practicable to pour ferro tungsten made in such manner, and enpedients are resorted to in order to get the mass of ferro tungsten out of the furnace, such as making the furnace in parts bolted together, so that the bolts can be removed and the furnace parts separated. After getting the ferro tungsten out of the furnace in this or equivalent ways, the button or mass is broken up. The process of breaking and crushing this mass of material to the size suitable for further use involves several successive operations which are laborious and expensive. After it is broken up, the fcrro tungsten is made use of for forming part of the charge in a steel furnace for making tungsten bearing steels, that is to say, steels containing tungsten, such as high speed steel, etc.

The most plentiful and cheapest grade of tungsten ore is wolframite, which in addition to the tungsten contained usually contains such quantities of tin and manganese as to be harmful if introduced into a tungsten bearing steel. A direct reduction of tungsten ore, such as that previously outlined, does not remove these impurities. On this account the tungsten ore which has ordinarily been used in a high grade comparatively expensive ore, such as sheelite, which is relatively free of impurities, or wolframite from which the impurities have been partially removed by some supplementary process.

Ferro tungsten, as heretofore made, has a very high melting point and a very high specific gravity as compared with the molten steel, and has a marked tendency to segregate in the bottom, thus prolonging the time of the heat and often requiring vigorous and laborious agitation of the bath in order to secure a comparatively uniform mixture of the tungsten with the other elements. This characteristic of ferro tungsten often results in a certain amount of tungsten being trapped in the lining or bottom of the steel making furnace which causes trouble in case the furnace is subsequently used for the production of some non-tungsten containing steel.

It is recognized by steel makers that the qualityof the steel in the ingot is directly related to the size of the ingot cast'and that as the size of the ingot increases thequality of the steel decreases. It is also recognized that a certain amount of mechanical work is necessary in reducing the ingot to the finished bar in order to refine the grain structure of the steel. This mechanical reduction being an expensive process, it is obvious that any unnecessary labor performed in reducing an ingot of larger size than necessary from a quality standpoint to the finished bar is uneconomical and such excess reduction in the rolls or under the hammer may easily affect the quality of the finished steel adversely.

Because of the difficulty of securing a uniform mixture of tungsten with steel by the old process that'has been described, the size of the electric furnace employed for making high speed steel and other similar steels has been limited in capacity to one from which a relatively few ingots of small size could be cast. I

By the process of the present invention, practically all of the objectionable features inherent in such prior practice are avoided;

According to our invention, the use of high grade ore is not important and practically any tungsten 'ore regardless of its tin or manganese content can be used without any supplementary treatment designed to remove these impurities.

As the first step, a portion of the tungsten ore or mixture of various ores is introduced into a preferably electric furnace with an excess of reducing agent, as coke, for example, and with fluxingimaterial, as'lime or soda or, less preferably, calcium carbide. In case of using calcium carbide, carbon in the form of coke or other form need not be used. A small quantity offluorspar is of advantage and serves to give greater fluidity in the smelted material. l/Vhere the ore contains manganese, tin, arsenic or the like in such proportions that removal thereof is of importance, sufficient soda, preferably soda ash, is used to effect a combination with-such undesirable elements.

In the operation of the furnace a relatively small button of ferro tungsten is first formed in the bottom and serves to maintain the necessary electrical contact.

As the operation proceeds, further portions oftungsten ore mixed with coke and fluxing material are added. In all additions, however, after the furnace has been once started, the amount of the reducing agent mixed with the ore is adjusted to prevent any further deposition of iron and tungsten in the metallic state. i

In this Way, while the tungsten is not reduced to the metallic state, a partial reduction takes place, and the manganese,,tin and arsenicare-combined with the soda ash.

As the operation proceeds the fluid material is tapped from the furnace. This tapping can be done at one level as the hot fluid material accumulates and the operation may be substantially continuous, new charging material being added after each tap.

The poured material so obtained and containing in the neighborhood of 50% tungsten is comparatively friable when cooled and is readily broken u In the next step of our process, the material so obtained is made use of for securing addition of tungsten to alloy steel, as, for example, it is introduced into an electric furnace charge in making tungsten bearing steel, as highspeed steel, for example.

According to the preferred mode of using this material in the manufacture of high speed or other tungsten bearing steels, a predetermined quantity of material is added in a cold or molten state to an electrlc steel making furnace in which has been previously prepared a molten bath of steel which may or may not contain other alloying elements. A calculated quantity of some reducing agent, such as ferro silicon or carbon is also added to effect the final reduction of the tungsten to the metallic state. This reduction takes place rapidly and the metallic tungsten so reduced forms a homogeneous alloy with the steel, the tungsten exhibiting little or no tendency to go to the bottom of the furnace. Without being confined to any particular theory as to this, our belief is that this desirabl csult is due in part to the tungsten containin material introduced into the furnace being of relatively low specific gravity, and in part to the tungsten metal when linally reduced being in highly subdivided state and even in a state of molecular subdivision.

Laboratory analyses show that when steel is manufactured by our improved process from tungsten ore containing relatively large percentages of tin and manganese and the process is carried out with the addition of soda ash as described, no appreciable quantities of tin and manganese are present in the finishe'd alloy steel, and all or practically all of the tungsten of the ore is to be found in the steel. l i here in working such impure ore, however, soda ash is omitted, not only do the m auganese and. tin of the ore enter into the steel, but the yield of tungsten is materially reduced, thus indicating that by our improved process a con'ibination is effected between the manganese and tin and the soda ash which remains behind in the slag of the steel furnace, while the tungsten is reduced in to the bath and further showing that when the soda ash is not used, tin and manganese are reduced into the bath leaving tungsten behind.

The described process has very many features of advantage and practically eliminates all the objectionable features inherent in prior practice. Cheap ores may be used, the furnace may be of any ordinary form, the partially reduced material is pourable, it is frangible and. readily broken into small pieces or it may be added in a molten state to the steel; it is practically carbon free. Its specific gravity is lower than that of molten steel. Its melting point is lower than that of the steel. The tungsten content is readily reduced to the metallic state. The manganese and tin are prevented from entering the steel. The steel produced in this manner is of uniform quality and analysis in the furnace.

It is possible by our process to pour successive portions of steel from one melt and to cast a much larger number of small ingots than was possible under the previous process. This characteristic of our process permits the use of a much. larger furnace than has heretofore been practical in making steels of the character described, and the size of ingots can be so controlled so as to get the necessary amount of grain refinement by hot mechanical working and avoid subjecting the steel to uneconomical and perhaps harmful excess mechanical Working for reduction in size or cross section.

It is possible to hold the alloy steel within relatively close limits of tungsten. The electric steel making furnace may be successively used for the production of tungsten bearing steels and non-tungsten bearing steels without contamination of the latter.

By our process a much larger percentage of tungsten contained in the ore is recovered, a yield as high as 98% of the tungsten in the ore having been recovered in some instances.

The process, which has been described, proceeds rapidly and substantially continuously and can be carried on in practically any desired quantities. The cost of power, fuel, labor and refractories are all greatly reduced and much time is saved, particularly in operation of the steel making furnace.

The present application is a continuation of our former application Serial No. 5,888, filed Jan. 30, 1925.

WVe claim:

1. A new metallurgical product adapted for use in making tungsten-containing alloy steels with approximately 100% tungsten recovery consisting of a frangible conglomerate comprising partially reduced oxide of tungsten and slag material comprising fixation combinations of impurities such as manganese, tin and arsenic with soda or soda ash, and which do not enter the steel when said conglomerate metallurgical product is introduced into the steel making furnace.

2. Metallurgical product obtained from tungsten ore containing tin, manganese and the like as undesirable constituents, comprising a frangible conglomerateconsisting predominately of partially reduced oxide of tungsten and containing fixation combinations of the impurities such as tin and manganese with basic material and which impurities do not enter the steel when said metallurgical product is introduced into the steel making process.

, 3. Processof producing from tungsten ore containing undesirable materials such as tin and manganese a product adapted when subjected to reduction in the steel making furnace to yield substantially only metallic iron and tungsten, which consists in heating such ore with basic material adapted to combine with the undesirables, and with reducing material, while adjusting the quantity of reducing material so as to avoid reduction of iron and tungsten to metallic state.

4. Process of producing from tungsten ore containing undesirable materials such as tin and manganese a product adapted when sub jected to reduction in the steel making furnace to yield substantially only metallic iron and tungsten, which consists in heating such ore with material. such as soda ash adapted to combine with the undesirables, and with reducing material, while adjusting the quantity of reducing material so as to avoid reduction of iron and tungsten to metallic state.

5. The process of making tungsten bearing alloy steel substantially free from undesirable material such as tin and manganese, from tungsten ores containing certain of such undesirable constituents in substantial propor tion, which comprises heating such ore with basic material adapted to combine with the undesirables and with reducing material while adjusting the quantity of the reducing material so as to avoid reduction of iron and tungsten to metallic state, and introducing the product so obtained as a part of the charge in steel making, and reducing the tungsten to the metallic state therein substantially without reduction from said treatedproduct of said undesirable constituents.

6. The process of making tungsten bearing alloy steel substantially free from undesirable material such as tin and manganese, from tungsten ores containing certain of such undesirable constituents in substantial proportion, which comprises heating such ore with material, such as soda ash adapted to combine with the undesirables, and with reducing material, while adjusting the quantity of the reducing material so as to avoid reduction of iron and tungsten to metallic state, and introducing the product so obtained as a part of the charge in steel making, and reducing the tungsten to the metallic state therein substantially without reduction from said treated product of said undesirable constituents. In testimony that we claim the foregoing, we have signed our names hereto.

HILAND G. BATCI-IELLER. JESS D. KELLEY. 

